The broad objective of this research project is to study the mechanism of the control of steroid biosynthetic pathways in the adrenal cortex by ACTH. Specifically, the mechanism by which ACTH stimulates cortisol production through increasing 17 alpha-hydroxylase enzyme activity in the rabbit adrenal gland will be investigated. Approaches and methodology to be used include: 1. Development of an in vitro cell- free or tissue superfusion system which will allow better evaluation of the effect of inhibitors of RNA, protein and heme biosynthesis on the 17 alpha-hydroxylase stimulating activity of ACTH than is afforded by in vitro studies. 2. Evaluation of the possible mediation of this action of ACTH by a 3', 5' -adenosine monophosphate. 3. Evaluation of the possible role of prostaglandins in this process. 4) Determination of whether or not DNA biosynthesis is required for this 17 alpha- hydroxylase stimulating activity of ACTH. 5) Measurement of cytochrome P-450 concentration in microsomes prepared from adrenal glands of ACTH- stimulated and control, non-stimulated rabbits to determine if the increased enzyme activity is accompanied by an increase in this cytochrome. 6) Measurement of cytochrome P-450 substrate binding difference spectra in adrenal microsomes from control and ACTH- stimulated rabbits to determine whether a difference or change in cytochrome P-450 substrate binding specificity can be demonstrated subsequent to ACTH stimulation.